Wheel position detection device
The wheel position detection device uses acceleration sensors to determine wheel positions efficiently, reducing power consumption by stopping unnecessary angle detection processes once positions are identified, addressing power inefficiencies in existing systems.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DENSO CORP
- Filing Date
- 2022-12-21
- Publication Date
- 2026-06-23
AI Technical Summary
Existing wheel position detection devices in vehicles consume excessive power due to continuous rotation angle detection by tire sensors after vehicle movement, leading to inefficient power usage.
A wheel position detection device that utilizes tire sensors with acceleration sensors to determine rotation angles and direction, allowing for one-way communication when the vehicle is moving and reducing power consumption by stopping unnecessary angle detection processes once wheel positions are determined.
The device effectively identifies wheel positions while significantly reducing power consumption in tire sensors by minimizing continuous angle detection during vehicle operation.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a wheel position detection device.
Background Art
[0002] Conventionally, Patent Document 1 discloses a technique for acquiring information indicating the tooth position of a gear based on a detection signal of a wheel speed sensor that detects the passage of the teeth of a gear, and identifying to which wheel a tire sensor that detects the air pressure of a tire is attached based on the acquired information. Specifically, after a control unit of the tire sensor detects an angle (rotation angle) of the tire sensor with respect to the center of the wheel based on a component of gravitational acceleration that changes as the wheel rotates, frame transmission is performed at a timing when the tire sensor reaches a predetermined angle, and the tooth position when the in-vehicle device provided on the vehicle body side receives the frame is acquired from the wheel speed sensor. Further, a variation allowable range is set based on the tooth position at the reception timing of the frame, and if the tooth position at the reception timing of a subsequent frame is outside the variation allowable range, it is excluded from the candidates for the wheel to which the tire sensor that transmitted the frame is attached. Then, the remaining wheel is registered as the wheel to which the tire sensor that transmitted the frame is attached.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Incidentally, the wheel position detection device described in Patent Document 1 uses one-way communication between the tire sensor and the on-board unit. Therefore, even after the vehicle starts moving and the wheel positions to which each tire sensor is attached are determined, the tire sensor continues to detect its rotation angle and transmit frames at the timing when a predetermined angle is reached. Detecting the rotation angle of the tire sensor requires observation and calculation of acceleration for a certain period of time or while the wheel rotates a certain number of times or more, which is undesirable as it results in wasted power consumption by the tire sensor.
[0005] The purpose of this disclosure is to provide a wheel position detection device that can identify the wheel position on which a tire sensor is installed while suppressing power consumption in the tire sensor. [Means for solving the problem]
[0006] The invention described in claim 1 is, A wheel position detection device applied to a vehicle (1) in which a plurality of wheels (5a to 5d), including tires, are attached to a vehicle body (6), Multiple tire sensors (2) are provided on each of the multiple wheels (5a to 5d) and transmit frames to which unique identification information is attached, The vehicle is equipped with an on-board device (3), Each of the multiple tire sensors includes an acceleration sensor (22) that outputs a detection signal corresponding to the acceleration that changes with the rotation of the wheel, a first control unit (23) that performs a series of processes to determine the rotation angle indicating the position of the tire sensor in the circumferential direction of the wheel as a first rotation angle based on the detection signal of the acceleration sensor when the acceleration sensor's detection signal is greater than or equal to a predetermined value, and to notify the in-vehicle unit of the first rotation angle, and a first transceiver (24) that transmits a frame and receives a response signal transmitted from the in-vehicle unit. The in-vehicle unit includes a second transceiver (31) that receives frames and transmits response signals, and a second control unit (33) that identifies the wheel position on which the tire sensor is installed based on the output signals of wheel angle sensors (11a to 11d) provided for each of the multiple wheels and notification of the first rotation angle. The second control unit notifies the tire sensor via the second transmitting / receiving unit of the wheel position determination status, indicating whether the wheel position is determined or not. When the first control unit is notified that the wheel position has been determined, it stops executing a series of processes during the driving state.
[0007] According to this, once the wheel position is determined by the on-board device, the series of processes performed by the tire sensor to detect the first rotation angle and notify the vehicle of that first rotation angle while the vehicle is in motion are stopped. Therefore, it is possible to realize a wheel position detection device that can identify the wheel position on which the tire sensor is installed while suppressing power consumption in the tire sensor.
[0008] Here, the method for notifying the in-vehicle device of the first rotation angle may be either by adding the first rotation angle at the time of notification to the transmission frame when notifying tire information, including tire pressure, or by timing the notification of tire information to coincide with the timing when the tire sensor reaches a predetermined first rotation angle. Therefore, if the execution of the series of processes is stopped, the former method will not add the first rotation angle to the frame, and the latter method will not be timed to coincide with the timing when the predetermined angle is reached.
[0009] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]
[0010] [Figure 1] This is a schematic diagram of the tire pressure monitoring system according to the first embodiment. [Figure 2] This is a block diagram of the tire sensor. [Figure 3]This is an explanatory diagram illustrating the relationship between the direction of wheel rotation and the output of the acceleration sensor. [Figure 4] This is a block diagram of the in-vehicle unit. [Figure 5] This flowchart shows the flow of control processing performed by the tire sensor. [Figure 6] This flowchart shows the flow of control processing performed by the in-vehicle system. [Figure 7] This is an explanatory diagram illustrating the position detection process when the left and right tires are swapped. [Figure 8] This is an explanatory diagram illustrating the registration status when the location detection process is performed. [Modes for carrying out the invention]
[0011] An embodiment of the present disclosure will be described with reference to Figures 1 to 8. In this embodiment, an example will be described in which a tire pressure monitoring system (hereinafter referred to as TPMS) including the wheel position detection device of the present disclosure is applied to a vehicle 1 having four wheels 5a to 5d as driving wheels. In Figure 1, the top of the page is the front of the vehicle 1, the bottom of the page is the rear of the vehicle 1, and the left-right direction of the page is the left-right direction of the vehicle 1. In the following, when describing the four wheels 5a to 5d separately, the four wheels 5a to 5d may be referred to as the left front wheel FL, the right front wheel FR, the left rear wheel RL, and the right rear wheel RR. Also, in Figure 1, each tire sensor 2 is referred to as "2A" for the one installed on the left front wheel FL, "2B" for the one installed on the right front wheel FR, "2C" for the one installed on the left rear wheel RL, and "2D" for the one installed on the right rear wheel RR.
[0012] As shown in Figure 1, the TPMS is mounted on the vehicle 1 and includes an on-board unit 3 which contains tire sensors 2, an electronic control unit for the TPMS (hereinafter referred to as TPMS-ECU), and a meter 4.
[0013] The TPMS includes a wheel position detection device that detects the wheel positions where each tire sensor 2 is attached. This wheel position detection device uses each tire sensor 2 and in-vehicle unit 3 provided in the TPMS, and performs wheel position detection using information from an electronic control unit for brake control (hereinafter referred to as brake ECU 10). The brake ECU 10 acquires wheel speed pulses obtained from the detection signals of wheel angle sensors 11a to 11d provided corresponding to each wheel 5a to 5d, and transmits this information to the in-vehicle unit 3 for wheel position detection.
[0014] The wheel angle sensors 11a to 11d are generally what are called wheel speed sensors. This sensor outputs a signal corresponding to the tooth position of a gear that rotates with the axle as a wheel speed pulse, but here it is called a "wheel angle sensor" because it is used to acquire the angle at which the tire sensor 2 exists with respect to the central axis of each wheel 5a to 5d. Also, the angle of the position where the tire sensor 2 exists with respect to the central axis of each wheel 5a to 5d is simply called the "angle of the tire sensor 2".
[0015] As shown in FIG. 1, the tire sensor 2 is attached to each wheel 5a to 5d, detects the air pressure etc. of the tire attached to the wheels 5a to 5d, and stores and transmits information regarding the tire air pressure indicating the detection result in a frame. The in-vehicle unit 3 is attached to the vehicle body 6 side in the vehicle 1, receives the frame transmitted from the tire sensor 2, and performs various processes and calculations etc. based on the information stored therein to detect the tire air pressure and wheel position. The tire sensor 2 creates a frame by, for example, FSK (Frequency Shift Keying), and the in-vehicle unit 3 reads the information in the frame by demodulating the frame.
[0016] As shown in FIG. 2, the tire sensor 2 includes a sensing unit 21, an acceleration sensor 22, a first microcomputer 23, and a first transceiver 24, and each unit is driven based on power supply from a battery not shown.
[0017] The sensing unit 21 includes a pressure sensor 21a and a temperature sensor 21b, and outputs a detection signal corresponding to the tire air pressure and a detection signal corresponding to the temperature. The acceleration sensor 22 is used to detect the position of the tire sensor 2 itself at the wheels 5a to 5d to which the tire sensor 2 is attached, that is, to detect the angle of the tire sensor 2 and to determine whether the vehicle 1 is running.
[0018] The acceleration sensor 22 of the present embodiment is composed of a two-axis acceleration sensor. The acceleration sensor 22 can detect the acceleration in the radial direction of the wheels 5a to 5d as the first acceleration and the acceleration in the circumferential direction of the wheels 5a to 5d as the second acceleration among the accelerations acting on the wheels 5a to 5d during the rotation of the wheels 5a to 5d.
[0019] The first microcomputer 23 constitutes the "first control unit" in the tire sensor 2. The first microcomputer 23 includes a CPU, a memory such as a ROM and a RAM, and an I / O. The first microcomputer 23 executes predetermined processing according to a program stored in the built-in memory. The memory stores individual ID information including unique identification information for identifying each tire sensor 2 and vehicle-specific identification information for identifying the host vehicle.
[0020] The first microcomputer 23 repeatedly transmits frames at a predetermined interval while the vehicle 1 is running. For example, when the first microcomputer 23 receives the detection signals from the pressure sensor 21a and the temperature sensor 21b, it processes the signals and, if necessary, processes them to obtain information on the tire air pressure.
[0021] Furthermore, the first microcomputer 23 monitors the detection signal from the acceleration sensor 22 and determines the angle of the tire sensor 2 and whether or not the vehicle is in motion. It then stores information regarding tire pressure and the angle of the tire sensor 2, along with the ID information of the tire sensor 2, within a frame. Once the first microcomputer 23 has created the frame, it transmits it from the first transceiver unit 24 to the in-vehicle unit 3 at a predetermined timing. Hereafter, the information including tire pressure and the angle of the tire sensor 2 will also be simply referred to as tire information.
[0022] The output of the acceleration sensor 22 includes acceleration based on centrifugal force (hereinafter referred to as centrifugal acceleration). Centrifugal acceleration changes depending on the rotation state of the wheels 5a to 5d. Therefore, the first microcomputer 23 removes the gravitational acceleration component from the output of the acceleration sensor 22 to calculate centrifugal acceleration and determines whether or not the vehicle is moving based on that centrifugal acceleration.
[0023] For example, the first microcomputer 23 determines that the vehicle 1 is in a driving state when the centrifugal acceleration is above a predetermined value. In this case, it performs unidirectional communication, periodically transmitting only frames from the tire sensor 2. That is, the first microcomputer 23 stores a unidirectional command within the frame and transmits the frame.
[0024] Furthermore, the first microcomputer 23 determines that the vehicle 1 is moving slowly or stopped if the centrifugal acceleration is below a specified value. In this case, in addition to transmitting a frame from the tire sensor 2, it performs bidirectional communication to request a response from the on-board unit 3. That is, the first microcomputer 23 stores bidirectional commands within the frame and transmits the frame. Note that in the acceleration-based driving determination, it is determined whether the acceleration is above a specified value or not, but instantaneous acceleration rises and so on are canceled out as noise.
[0025] Furthermore, since the acceleration sensor 22 outputs a detection signal corresponding to the rotation of each wheel 5a to 5d, when the vehicle is in motion, the detection signal includes a component of gravitational acceleration, resulting in a signal with an amplitude corresponding to the wheel rotation. Therefore, the position of the acceleration sensor 22, i.e., the angle of the tire sensor 2, can be determined based on this amplitude.
[0026] For example, the first microcomputer 23 calculates its own rotational angle as the first rotational angle based on the gravitational acceleration component included in the detection signal of the acceleration sensor 22. The first rotational angle is defined as the rotational angle at which the tire sensor 2 is located, with any rotational angle in the circumferential direction around the central axis of the wheels 5a to 5d of the tire sensor 2 being 0°, for example, when the tire sensor 2 is in its lowest position being 0°. In this case, the first rotational angle can be represented as 180° when the tire sensor 2 is at its apex, and 90° and 270° when it is in a horizontal position, respectively.
[0027] Here, when the wheels 5a to 5d rotate in one direction in the circumferential direction, for example as shown in Figure 3(a), the second acceleration tends to increase when the first acceleration is "+1G", and decreases when the first acceleration is "-1G". Also, when the wheels 5a to 5d rotate in the other direction in the circumferential direction, for example as shown in Figure 3(b), the second acceleration tends to decrease when the first acceleration is "+1G", and increases when the first acceleration is "-1G". Based on these trends, the first microcomputer 23 detects the rotation direction of the wheels 5a to 5d based on the first and second accelerations detected by the acceleration sensor 22. In this way, the tire sensor 2 of this embodiment is able to recognize not only its own rotation angle but also its rotation direction.
[0028] Furthermore, when attaching or detaching wheels from the vehicle body 6, unique vibration patterns and changes in the direction of gravity occur due to operations such as rotation (for example, tilting or rotating the wheels). Some of the acceleration changes resulting from these can not occur during driving, and can therefore be distinguished from those that occur during driving. Taking this into consideration, the first microcomputer 23 of this embodiment is configured to detect the attachment or detachment of wheels from the vehicle body 6 based on the detection signal from the acceleration sensor 22.
[0029] While it may be technically possible to actively detect whether the wheels have been removed or reattached, this is not practical from the standpoint of battery consumption. On the other hand, if there is almost no vibration while vehicle 1 is parked, it can be presumed that the wheels have not been removed or reattached.
[0030] Based on these considerations, the first microcomputer 23 of this embodiment determines that the wheel has not been attached or detached if the vibration detected by the acceleration sensor 22 is below a reference value. In reality, even when the vehicle 1 is parked, the acceleration sensor 22 may detect vibrations from passengers getting in and out, ground shaking, or loud noises. For this reason, the reference value used as the determination criterion is set based on vibrations detected by the acceleration sensor 22 when passengers get in and out, ground shaking, or loud noises occur. Unlike the driving determination based on acceleration, the wheel attachment / detachment determination determines the presence or absence of a peak value of high-frequency acceleration change.
[0031] The first transmitting / receiving unit 24 comprises a first transmitting / receiving circuit 241 and a first communication antenna 242. The first transmitting / receiving circuit 241 functions as an output unit that transmits frames received from the first microcomputer 23 to the in-vehicle unit 3 via the first communication antenna 242. The first transmitting / receiving unit 24 also functions as an input unit that demodulates response signals from the in-vehicle unit 3 and sends them to the first microcomputer 23. Although the first transmitting / receiving unit 24 is described here as a single configuration, the transmitting and receiving units may be configured separately. In this example, the first transmitting / receiving unit 24 transmits and receives using radio waves in the UHF band of, for example, 300 MHz or 400 MHz, but the frequency band of radio waves used can be arbitrarily selected.
[0032] The battery supplies power to the sensing unit 21, acceleration sensor 22, first microcomputer 23, etc. Power from this battery is used to collect tire pressure data in the sensing unit 21 and to perform various calculations in the first microcomputer 23. Note that the power source for the tire sensor 2 may be a power generator and / or a storage battery instead of a battery. While a power generator configuration reduces battery life issues compared to a battery, generating large amounts of power is difficult, so the challenge of reducing power consumption remains, similar to the battery configuration.
[0033] The tire sensor 2 configured in this way is attached, for example, to the air injection valve on the wheel of each wheel 5a to 5d, and is positioned so that the sensing unit 21 is exposed on the inside of the tire. As a result, the tire sensor 2 detects the tire pressure of the corresponding wheel and the angle of the tire sensor 2, and transmits a frame at a predetermined timing via the first communication antenna 242 provided on each tire sensor 2.
[0034] On the other hand, the on-board unit 3 is installed in the vehicle body 6. As shown in Figure 4, the on-board unit 3 includes a second transceiver 31 and a second microcomputer 33, etc. The on-board unit 3 acquires wheel speed pulses from the brake ECU 10 via an in-vehicle LAN (Local Area Network) such as CAN (Controller Area Network), as described later, and obtains the tooth position, indicated by the number of edges or teeth, of the gears that rotate together with each wheel 5a to 5d. In the following explanation, the number of edges will be used as an example to describe the gear information, but the number of teeth can also be used.
[0035] The second transmitting / receiving unit 31 comprises a second communication antenna 311 and a second transmitting / receiving circuit 312. The second transmitting / receiving circuit 312 functions as an input unit, receiving transmission frames from each tire sensor 2 received by the second communication antenna 311 and sending those frames to the second microcomputer 33. The second transmitting / receiving circuit 312 also functions as an output unit, transmitting a response signal corresponding to the frame received from the tire sensor 2 towards the tire sensor 2. Although the second transmitting / receiving unit 31 is described here as a single configuration, the transmitting and receiving units may be configured separately.
[0036] The second microcomputer 33 constitutes the "second control unit" in the in-vehicle unit 3. The second microcomputer 33 is equipped with a CPU, memory such as ROM and RAM, I / O, etc. The second microcomputer 33 executes TPMS specification processing, including wheel position detection processing and tire pressure detection processing, according to the program stored in its internal memory.
[0037] In the wheel position detection process, wheel position detection is performed to determine which of the wheels 5a to 5d the tire sensor 2 is attached to. The second microcomputer 33 performs wheel position detection, for example, based on the output signals of each wheel angle sensor 11a to 11d and the notification of the first rotation angle mentioned above.
[0038] The tire pressure detection process detects the tire pressure of wheels 5a to 5d to which each tire sensor 2 is attached. Specifically, the second microcomputer 33 associates and stores the ID information of each tire sensor 2 with the position of each wheel 5a to 5d to which each tire sensor 2 is attached, based on the results of wheel position detection. Subsequently, it detects the tire pressure of each wheel 5a to 5d by calculating the equivalent tire pressure value at a predetermined temperature based on the ID information and tire information stored in the transmission frame from each tire sensor 2. Then, it outputs an electrical signal corresponding to the tire pressure detection result to the meter 4 via the in-vehicle LAN such as CAN. For example, the second microcomputer 33 outputs a signal indicating the tire pressure of each wheel 5a to 5d to the meter 4. The second microcomputer 33 also detects a decrease in tire pressure by comparing the tire pressure with a predetermined judgment threshold, and outputs a signal to that effect to the meter 4 when a decrease in tire pressure is detected. This allows the meter 4 to be notified if the tire pressure of any of the four wheels 5a-5d has decreased, and this is then displayed on the meter 4.
[0039] Meter 4 is a display unit located inside the vehicle cabin that displays various information. Meter 4 is powered on when the vehicle's start switch is turned on, and displays various information when the power is on. The display by Meter 4 is basically performed when the power is on.
[0040] As shown in Figure 1, the meter 4 is positioned in a location visible to the driver and consists of, for example, a multi-information display or navigation system display installed in the instrument panel of the vehicle 1. When the meter 4 receives a signal from, for example, the second microcomputer 33 in the in-vehicle unit 3 indicating that the tire pressure has decreased, it identifies the relevant wheels 5a to 5d and displays a message indicating the decrease in tire pressure to the driver.
[0041] Next, the wheel position detection process performed in the TPMS of this embodiment will be described. First, the process on the tire sensor 2 side will be described with reference to Figure 5, and then the process on the in-vehicle device 3 side will be described with reference to Figure 6. The control flow shown in Figure 5 is executed by the first microcomputer 23 of the tire sensor 2 at a predetermined control cycle.
[0042] As shown in Figure 5, step S100 determines whether the acceleration is equal to or greater than a specified value. Here, acceleration refers to the centrifugal acceleration obtained from the detection signal of the acceleration sensor 22, and the specified value is assumed to be the centrifugal acceleration that occurs during low-speed driving of, for example, about 30 km / h. In the following explanation as well, the acceleration being compared with the specified value refers to the centrifugal acceleration. If the determination is positive, vehicle 1 enters a driving state; if the determination is negative, it enters a slow-moving or stopped state.
[0043] If a positive result is obtained in step S100, the process proceeds to step S105, where a first timer is set to a driving interval, for example, every 60 seconds, so that a frame is transmitted at each periodic transmission cycle set while vehicle 1 is in motion.
[0044] Next, the process proceeds to step S110, where the on-board unit 3 determines whether the wheel position of the tire sensor 2 is being determined or not. Specifically, the tire sensor 2 determines whether the wheel position is being determined or not by referring to status flags indicating whether the wheel position is determined or not.
[0045] As described later, the TPMS transmits a frame containing bidirectional commands from the tire sensor 2, and when this is received by the on-board unit 3, the on-board unit 3 sends a response signal. This response signal includes a wheel position determination status indicating whether the wheel position is determined or not. The tire sensor 2 basically sets a status flag based on the wheel position determination status included in the response signal.
[0046] If step S110 is a negative result, the process proceeds to step S115, where an angle detection process is performed to determine the first rotation angle, which is the angle of the tire sensor 2. In the angle detection process, as described above, the rotation angle at which the system is located is calculated as the first rotation angle based on the gravitational acceleration component included in the detection signal of the acceleration sensor 22.
[0047] After storing the first rotation angle in memory, the tire sensor 2 proceeds to step S120 and performs a rotation direction detection process to detect the rotation direction of the wheels 5a to 5d to which the tire sensor 2 is attached. As described above, this rotation direction detection process detects the rotation direction of the wheels 5a to 5d based on the first and second accelerations detected by the acceleration sensor 22. In this embodiment, when the wheels 5a to 5d rotate in one direction in the circumferential direction, it is defined as forward rotation CW, and when they rotate in the other direction in the circumferential direction, it is defined as reverse rotation CCW.
[0048] The tire sensor 2 stores the rotation direction of wheels 5a to 5d in memory, and then proceeds to step S125. In step S125, a frame containing tire information, including tire pressure, first rotation angle, rotation direction of wheels 5a to 5d, and the setting of the attachment / detachment flag described later, is transmitted. At this time, since the frame is transmitted when it is determined that the vehicle 1 is moving because the centrifugal acceleration is above a specified value, a unidirectional command is stored in the frame.
[0049] If step S110 is a positive result, the wheel position is determined, so the series of processes necessary to identify the wheel position, such as the angle detection process in step S115 and the rotation direction detection process in step S120, are skipped, and the process proceeds to step S125. In this case, in step S125, a frame containing tire information, including tire pressure, is transmitted.
[0050] After the frame is transmitted, the process proceeds to step S130, where it is determined whether the acceleration is above a specified value. This process is repeated until the first timer, set in step S105 as the driving interval, expires, confirming that vehicle 1 is continuing to drive. Then, in step S135, when the timer expires, the process returns to step S105. As a result, while vehicle 1 is driving, a frame containing a unidirectional command is transmitted at predetermined intervals set as the driving interval.
[0051] On the other hand, if a negative result is obtained in step S100 or step S130, the process proceeds to step S140. In step S140, a second timer is set to a predetermined reference time, and the process proceeds to step S145. The reference time is a time that is assumed to be sufficiently long compared to the typical stopping time that occurs when waiting at a traffic light, etc., and is set to, for example, 15 minutes.
[0052] In the following step, S145, the wheel removal flag is set to "Not Performed," indicating that the wheel removal has not yet been carried out. This process resets the wheel removal flag to "Not Performed" at the moment when vehicle 1 switches from a driving state to a slow-moving / stopped state.
[0053] Next, the process proceeds to step S150, where the first timer is set to a longer stopping interval than the driving interval, for example, every 120 seconds, so that a frame is transmitted at each set periodic transmission interval while the vehicle is stopped. Then, the process proceeds to step S155, where a frame containing detection data regarding tire pressure is transmitted. In step S155, a frame containing tire information, including tire pressure and the setting of the detachment flag, is transmitted. Also, since this is a frame transmission while the vehicle is moving slowly or stopped, bidirectional commands are stored within the frame.
[0054] As will be described later, a frame containing bidirectional commands is transmitted from the tire sensor 2, and when it is received by the in-vehicle unit 3, a response signal is transmitted from the in-vehicle unit 3. Therefore, in step S160, it is determined whether or not a response reception has occurred and whether or not a response signal has been received. In this determination, if a response signal has been received from the in-vehicle unit 3, it is determined to be positive, and if a response signal has not been received, it is determined to be negative.
[0055] If a positive result is obtained in step S160, the process proceeds to step S165, where the on-board unit 3 determines whether the wheel position of the tire sensor 2 is being determined or not. In this embodiment of the TPMS, the response signal is accompanied by a wheel position determination state indicating whether the wheel position is determined or not. Therefore, the tire sensor 2 determines whether the wheel position is being determined or not based on the wheel position determination state accompanied by the response signal.
[0056] If the wheel position is being determined, the process proceeds to step S170, where a status flag is set to indicate that the wheel position is being determined. If the wheel position is not yet determined, the process proceeds to step S175, where a status flag is set to indicate that the wheel position is not yet determined. This status flag may be set to either on or off when the wheel position is being determined, and to either on or off when the wheel position is not yet determined.
[0057] After the status flag is set in step S170 or step S175, the process proceeds to step S180. If a response signal from the in-vehicle unit 3 has not been received, it is determined to be negative in step S160, and the process proceeds to step S180.
[0058] In step S180, it is determined whether the first timer has timed out. If the first timer has timed out, step S180 is deemed positive, and the process returns to step S150. If the first timer has not timed out, the process proceeds to step S185, where it is determined whether the second timer has timed out.
[0059] If the second timer has not expired, step S185 is deemed invalid, and the process proceeds to step S190, where it is determined whether the acceleration is above or below the specified value. If the acceleration is above or below the specified value, the process returns to step S105; if the acceleration is below the specified value, the process returns to step S180.
[0060] On the other hand, when the second timer expires, the process proceeds to step S195. The reference time set for the second timer is set to be sufficiently long compared to waiting at traffic lights, etc., so when the second timer expires, it is assumed that the parking has continued for a certain period of time. In such cases, it is possible that the rotation work of wheels 5a to 5d has been performed. For this reason, in step S195, a status flag is set to indicate that the wheel positions are not yet determined. As a result, when the vehicle 1 resumes driving, a series of processes necessary for determining the wheel positions, such as the angle detection process in step S115 and the rotation direction detection process in step S120, are performed.
[0061] After the status flag is set in step S195, the process proceeds to step S200, where it is determined whether or not there was vibration exceeding a certain threshold to determine whether or not the wheel removal / installation has been performed. If there is no vibration exceeding the threshold, it is presumed that the wheel removal / installation has not been performed, so step S205 is skipped and the process proceeds to step S190. On the other hand, if there is vibration exceeding the threshold, it is possible that the wheel removal / installation has been performed. Therefore, if there is vibration exceeding the threshold, the process proceeds to step S205, the removal / installation flag is set to "unknown", and then the process proceeds to step S190. The status flag setting is notified to the in-vehicle unit 3 through frame transmission in steps S125 and S155.
[0062] This concludes the explanation of the processing on the tire sensor 2 side. Below, the processing on the in-vehicle unit 3 side will be explained with reference to Figure 6. The control flow shown in Figure 6 is executed by the second microcomputer 33 of the in-vehicle unit 3 at a predetermined control cycle.
[0063] As shown in Figure 6, first, in step S300, it is determined whether the start switch is ON or OFF. If this is determined to be true, the process proceeds to step S305, and the reception process begins. This makes it possible to receive frames transmitted from each tire sensor 2.
[0064] Next, once the reception process begins, the system proceeds to step S310 to determine whether or not there is vehicle speed. This determination of whether or not there is vehicle speed is based on the detection signals from the wheel angle sensors 11a to 11d.
[0065] If there is no vehicle speed, the determination is negative in step S310, and the process proceeds to step S315, where it is determined whether or not the timer for measuring the duration of the vehicle 1's stationary state is operating. If the timer is not running, proceed to step S320; if the timer is running, skip step S320 and proceed to step S325.
[0066] In step S320, a timer is set for a predetermined parking judgment time, and then the process proceeds to step S325. The parking judgment time set here is, like the reference time, a time that is assumed to be sufficiently long compared to the typical stopping time that occurs when waiting at traffic lights, etc. The parking judgment time is set to, for example, 15 minutes. Note that the parking judgment time may be set to the same time as the reference time, or to a different time.
[0067] In the following step S325, it is determined whether the timer has expired. The parking detection time set for the timer is set to be sufficiently long compared to waiting at traffic lights, etc., so if the timer expires, it means that the parking has continued for a certain period of time. In this case, it is possible that wheel rotation work 5a to 5d has been performed.
[0068] Therefore, if the timer expires, a positive result is obtained in step S325, and the process proceeds to step S330, where the wheel position determination state is set to indicate that the wheel position is not yet determined. After that, the process proceeds to step S345. If the timer has not expired, a negative result is obtained in step S325, and the process skips step S330 and proceeds to step S345.
[0069] On the other hand, if there is vehicle speed, a positive determination is made in step S310, and the process proceeds to step S335, where the timer is stopped. Then, the process proceeds to step S340, where it is determined whether wheel position detection is necessary. In this determination process, if the wheel position of each tire sensor 2 is identified in the wheel position detection of the TPMS standard processing described later, it is determined that wheel position detection is unnecessary. Also, if wheel position detection is unnecessary based on the tire information attached to the frame from the tire sensor 2, it is determined that wheel position detection is unnecessary. For example, if the tire information attached to the frame indicates that the wheels have not been removed or attached, and that the rotation direction of wheels 5a to 5d has not changed, it is determined that wheel position detection is unnecessary.
[0070] On the other hand, if the wheel position of at least one tire sensor 2 is not identified during the TPMS standard processing described later, it is determined that wheel position detection is necessary. Furthermore, if wheel position detection is necessary based on the tire information attached to the frame from the tire sensor 2, it is determined that wheel position detection is necessary. For example, if the tire information attached to the frame indicates that the wheel attachment / detachment status is unknown, it is determined that wheel position detection is necessary.
[0071] After determining whether wheel position detection is necessary, the process proceeds to step S345, where it is determined whether a command has been received, that is, whether a unidirectional or bidirectional command included in the frame transmitted from each tire sensor 2 has been received. Since the frame transmission timing differs for each tire sensor 2, the determination in step S345 is performed for each frame transmitted from each tire sensor 2.
[0072] If neither a unidirectional nor a bidirectional command is received, the process returns to step S300; if either a unidirectional or bidirectional command is received, the process proceeds to step S350.
[0073] In step S350, it is determined whether the received command is a bidirectional command. If a frame is received from the tire sensor 2 at regular transmission intervals set by the stopping interval while the vehicle is moving slowly or stopped, it is determined to be a bidirectional command, and therefore a positive determination is made in step S350. In that case, the process proceeds to step S355, and a response signal with added information such as the wheel position identification status is transmitted. The wheel position identification status is information indicated as a flag, etc. The wheel position identification status is set to "confirmed" if the wheel positions of all tire sensors 2 have been identified, and to "unconfirmed" if the wheel position of at least one tire sensor 2 has not been identified. The wheel position identification status may also include individual information indicating whether the wheel position of each tire sensor 2 has been identified or not.
[0074] Thus, when the power switch is turned on and a frame containing a bidirectional command is received, a signal with added information such as the wheel position determination status is sent as a response signal to the frame. This notifies the tire sensor 2 that sent the frame containing the bidirectional command whether the wheel position is determined or not.
[0075] Here, the frame indicating the bidirectional command basically includes the result of whether or not the wheel has been removed or attached. If the wheel removal / attachment determination result shown in the frame indicates that the wheel has not been removed or attached, wheel position detection may not be performed by the TPMS standard processing. In such cases, the on-board unit 3 adds the previously set wheel position identification state to the response signal and notifies the tire sensor 2 via the second transceiver unit 31.
[0076] After sending the response signal in step S355, the process proceeds to step S360. If the received command is a unidirectional command, a negative determination is made in step S350, and the process proceeds to step S360.
[0077] In step S360, the tire information attached to the received frame is stored in the memory of the second microcomputer 33. Regarding the rotation direction of wheels 5a to 5d, the information received with the unidirectional command just before switching to the slow-speed / stopped state is stored in memory. In addition, regarding the attachment and detachment of the wheels, the information received with the bidirectional command when the vehicle enters the slow-speed / stopped state is stored in memory.
[0078] After storing the tire information in memory, the process proceeds to step S365 to perform the TPMS standard processing. Here, the TPMS standard processing includes tire pressure detection processing, which includes displaying tire pressure, detecting abnormalities, and issuing alarms, as well as wheel position detection processing. After the TPMS standard processing is complete, the process returns to step S300.
[0079] Here, the wheel position detection process performed by the in-vehicle unit 3 will be described. The wheel position detection process is performed, for example, when the wheel position determination state is not yet determined. The in-vehicle unit 3 performs the normal position detection process, for example, when the wheels have not yet been attached or when the detection results of the rotation direction of the wheels 5a to 5d by the two tire sensors 2 do not indicate a reversal of the rotation direction.
[0080] In the normal position detection process, wheel position detection is performed based on the output signals from each wheel angle sensor 11a to 11d obtained from the brake ECU 10 and the first rotation angle notified from each tire sensor 2.
[0081] As a normal position detection process, for example, the wheel position detection process disclosed in Japanese Patent Publication No. 2010-122023 can be employed. Briefly explaining this process, the on-board unit 3 monitors the change in the relative angle between the first rotation angle included in the frame and the second rotation angle based on the output signals of each wheel angle sensor 11a to 11d at the time the frame indicating the first rotation angle is received. Then, while the vehicle 1 is running, any wheels 5a to 5d to which the tire sensor 2 that transmitted the frame is attached that have a relative angle change exceeding an allowable value are excluded from the candidates, and the remaining ones are identified as the wheels 5a to 5d to which the tire sensor 2 that transmitted the frame is attached. Note that the normal position detection process is not limited to the above, and for example, the wheel position detection process disclosed in Japanese Patent Publication No. 5910402 may also be employed. Briefly explaining this process, the on-board unit 3 transmits the frame at the timing when the first rotation angle becomes a specified angle while the vehicle is running, and obtains the tooth position at the time of receiving the frame indicating this first rotation angle from the wheel angle sensors 11a to 11d. Then, if the tooth position at the time of frame reception is outside the allowable variation range, it is excluded from the candidates for the wheel 5a-5d to which the tire sensor 2 that transmitted the frame is attached, and the remaining ones are identified as the wheel 5a-5d to which the tire sensor 2 that transmitted the frame is attached.
[0082] In this way, once the vehicle-mounted unit 3 identifies which of the wheels 5a to 5d each tire sensor 2 is attached to, it stores the ID information of each tire sensor 2 that transmitted the frame, associating it with the position of the wheel 5a to 5d to which it is attached. In addition, the vehicle-mounted unit 3 sets the wheel position identification state to confirmed. The wheel position identification state set here is added to the response signal in step S355 and notified to the tire sensor 2. With these steps, wheel position detection is completed.
[0083] On the other hand, if the removal or attachment of the wheels is unknown, and the detection results of the rotation direction of the two tire sensors 2 for the wheels 5a to 5d indicate a reversal of the rotation direction, the in-vehicle unit 3 is likely to have performed a rotation of the left and right wheels 5a to 5d. In this case, a position detection process different from the usual is performed. In this position detection process, the wheel positions of the two tire sensors 2 that indicate a reversal of the rotation direction are swapped to identify the wheels 5a to 5d to which the tire sensors 2 are attached.
[0084] Here, we will explain the position detection process when the left rear wheel RL and the right rear wheel RR are swapped during a rotation operation while vehicle 1 is parked, with reference to Figures 7 and 8. Note that Figures 7 and 8 are examples.
[0085] Assuming that the in-vehicle unit 3 immediately before parking has registered the following settings, as shown in the upper part of Figure 7: tire sensor 2 with "ID1" is on the left front wheel FL, tire sensor 2 with "ID2" is on the right front wheel FR, tire sensor 2 with "ID3" is on the left rear wheel RL, and tire sensor 2 with "ID4" is on the right rear wheel RR. In this state, if the left rear wheel RL and the right rear wheel RR are swapped during the rotation process, the wheel positions of tire sensors 2 with ID3 and ID4 will be swapped.
[0086] After the rotation work is completed and vehicle 1 starts moving, the on-board unit 3 receives tire information from each tire sensor 2, including tire pressure, rotation direction of wheels 5a to 5d, and a detachment flag. Based on the tire information received from each tire sensor 2, the on-board unit 3 determines whether the detachment of the wheels is unknown and whether the rotation direction detection results of the two tire sensors 2 for wheels 5a to 5d indicate a reversal of the rotation direction.
[0087] For example, as shown in the middle of Figure 7, when the in-vehicle unit 3 receives tire information from tire sensors 2 with ID1 and ID3, the in-vehicle unit 3 recognizes that the rotation direction of tire sensor 2 with ID3 has reversed and that it is unclear whether the wheel has been removed or attached.
[0088] Next, as shown in the lower part of Figure 7, when the in-vehicle unit 3 receives tire information from tire sensors 2 of ID2 and ID4, the rotation direction of tire sensor 2 of ID4 is reversed, and the in-vehicle unit 3 determines that it is unclear whether the wheel has been removed or attached.
[0089] In this case, the detachment status of the wheels is unknown, and the detection results of the rotation direction of the wheels 5a to 5d by the two tire sensors 2, ID3 and ID4, indicate a reversal of the rotation direction. Therefore, the in-vehicle unit 3 swaps the wheel positions of the tire sensors 2 ID3 and ID4, as shown in Figure 8.
[0090] In this way, once the vehicle-mounted unit 3 identifies which of the wheels 5a to 5d each tire sensor 2 is attached to, it stores the ID information of each tire sensor 2 in association with the position of the wheel 5a to 5d to which it is attached. In addition, the vehicle-mounted unit 3 sets the wheel position identification state to confirmed. The wheel position identification state set here is added to the response signal in step S355 and notified to the tire sensor 2. With these steps, wheel position detection is completed.
[0091] This completes the process when the start switch for vehicle 1 is ON. If the start switch for vehicle 1 is OFF, the determination in step S300 is negative, and the process proceeds to step S370, stopping the reception process.
[0092] Then, the process proceeds to step S375 to determine whether the start switch is ON or OFF. If the start switch is ON, step S375 is evaluated as positive, and the process proceeds to step S305 to resume receiving. On the other hand, if the start switch is OFF, step S375 is evaluated as negative, and the process proceeds to step S380.
[0093] In step S380, it is determined whether the timer has expired. As mentioned above, if the timer has expired, it is possible that the rotation operation of wheels 5a to 5d is being performed.
[0094] Therefore, if the timer expires, the process proceeds to step S385, where the wheel position determination state is set to indicate that the wheel position is not yet determined. After that, the process returns to step S375. If the timer has not expired, the process is negated in step S380, and the process skips step S385 and returns to step S375.
[0095] The TPMS described above includes a wheel position detection device. The wheel position detection device comprises a plurality of tire sensors 2, each provided on a plurality of wheels 5a to 5d, which transmit frames to which unique identification information is attached, and an on-board unit 3 provided on the vehicle 1.
[0096] Each of the multiple tire sensors 2 determines the rotation angle indicating the position of the tire sensor 2 in the circumferential direction of the wheels 5a to 5d as the first rotation angle based on the detection signal of the acceleration sensor 22 when the detection signal of the acceleration sensor 22 is greater than or equal to a predetermined value during driving. Then, it performs a "series of processes" to notify the in-vehicle unit 3 of the first rotation angle.
[0097] The onboard unit 3 notifies the tire sensor 2 via the second transmitting / receiving unit 31 of the wheel position determination status, indicating whether the wheel position is determined or not (see, for example, steps S345 to S355 in Figure 6). When each of the multiple tire sensors 2 is notified that the wheel position has been determined, it stops executing a series of processes in the driving state (see, for example, steps S100 to S125 in Figure 5).
[0098] According to this, once the wheel position is determined by the on-board unit 3, the series of processes performed by the tire sensor 2, such as detecting the first rotation angle and notifying the vehicle 1 of the first rotation angle while the vehicle 1 is in motion, are stopped. Therefore, the wheel position on which the tire sensor 2 is installed can be determined while suppressing power consumption in the tire sensor 2.
[0099] Furthermore, the wheel position detection device of this embodiment has the following features.
[0100] (1) When the in-vehicle unit 3 receives a frame, it transmits a response signal to the tire sensor 2 with the wheel position identification state added to it via the second transmitting / receiving unit 31 (see, for example, steps S345 to S355 in Figure 6). By notifying the tire sensor 2 of the wheel position identification state by adding the wheel position identification state to the response signal in this way, the tire sensor 2 does not need to be in a state where it can constantly receive signals including the wheel position identification state, and thus the power consumption of the tire sensor 2 can be suppressed.
[0101] (2) After determining the wheel positions, if the vehicle 1 remains stationary for longer than a predetermined parking determination time, the second microcomputer 33 changes the wheel position determination state to wheel position undetermined (see, for example, steps S310 to S330 and steps S380 to S385 in Figure 6).
[0102] If vehicle 1 remains stationary for a certain period of time, there is a possibility that wheels 5a to 5d are rotating. Considering this, it is desirable that, after the wheel positions are determined, if vehicle 1 remains stationary beyond the parking determination time, the wheel position determination state be changed to wheel position undetermined. In this case, if there is a possibility that wheels 5a to 5d are rotating, the series of processes performed by tire sensor 2 necessary for determining the wheel positions can be resumed.
[0103] (3) The first microcomputer 23 determines whether to perform a series of processes by referring to a status flag indicating whether the wheel position is determined or not in the running state of the vehicle 1 (see, for example, step S110 in Figure 5). In addition, when the determination of the wheel position is notified, the status flag is set to "wheel position determined" (see, for example, steps S165 and S170 in Figure 5).
[0104] On the other hand, if, after notification that the wheel position has been determined, the detection signal from the acceleration sensor 22 remains below a specified value for a predetermined reference time, the status flag is changed to "wheel position not determined" (see, for example, steps S185 to S190 in Figure 5).
[0105] Interference or other factors may prevent the notification of the wheel position determination status from the on-board unit 3 to the tire sensor 2. Therefore, it is desirable that the tire sensor 2 changes its status flag to "wheel position undetermined" if the detection signal from the acceleration sensor 22 remains below a specified value for a period of time exceeding a standard time. This would allow the tire sensor 2 to resume the series of processes necessary for determining the wheel position, even if the notification of the wheel position determination status from the on-board unit 3 to the tire sensor 2 fails when there is a possibility of wheel rotation of wheels 5a to 5d.
[0106] (4) The first microcomputer 23 creates a frame indicating a unidirectional command when transmitting a frame from the first transceiver unit 24 while the vehicle 1 is in motion (see, for example, step S125 in Figure 5). It also creates a frame indicating a bidirectional command requesting a response signal when the detection signal from the acceleration sensor 22 falls below a specified value (see, for example, step S155 in Figure 5).
[0107] If some tire sensors 2 are communicating bidirectionally with the on-board unit 3 while vehicle 1 is in motion, communication between other tire sensors 2 and the on-board unit 3 may be restricted, potentially preventing notifications such as abnormal tire pressure from reaching the on-board unit 3. Furthermore, constant bidirectional communication between tire sensors 2 and the on-board unit 3 increases the power consumption of the tire sensors 2. Considering these factors, it is desirable that the tire sensors 2 create a frame indicating a unidirectional command during driving conditions and create a frame indicating a bidirectional command when the detection signal from the acceleration sensor 22 falls below a specified value.
[0108] (5) The first microcomputer 23 determines whether the wheel has been attached or not when the detection signal from the acceleration sensor 22 falls below a specified value (see, for example, step S200 in Figure 5). The first transceiver 24 then transmits a frame indicating this determination result (see, for example, steps S125 and S155 in Figure 5).
[0109] The second microcomputer 33 determines whether it is necessary to identify the wheel position, including the result of determining whether the wheel has been attached or detached (see, for example, step S340 in Figure 6). If it is determined that it is not necessary to identify the wheel position, the second transmitting / receiving unit 31 notifies the tire sensor 2 of the wheel position identification status, indicating that the wheel position has been determined (see, for example, step S355 in Figure 6).
[0110] If it is determined that the wheels have not been removed or attached while Vehicle 1 is stationary, the wheel position to which the tire sensor 2 is attached will not change. Therefore, it is desirable to stop the series of processes performed by the tire sensor 2 necessary for determining the wheel position when it is determined that the wheels have not been removed or attached while Vehicle 1 is stationary, in order to suppress the power consumption of the tire sensor 2.
[0111] (6) However, while it is technically possible for the tire sensor 2 to actively detect the removal and installation of the wheel, the resulting increase in power consumption makes this practically difficult. For this reason, it is desirable that the tire sensor 2 be configured to determine whether or not the wheel has been removed or installed.
[0112] (7) The acceleration sensor 22 is capable of detecting the radial acceleration of the wheels 5a to 5d as the first acceleration and the circumferential acceleration of the wheels 5a to 5d as the second acceleration. The first microcomputer 23 detects the rotation direction of the wheels 5a to 5d based on the first and second accelerations detected by the acceleration sensor 22 when the vehicle 1 is running (see, for example, step S120 in Figure 5). The first transceiver 24 transmits a frame containing the detection result regarding the rotation direction of the wheels 5a to 5d (see, for example, step S125 in Figure 5).
[0113] The second microcomputer 33, if it indicates that there is a possibility of wheel removal or attachment for the two tire sensors 2, and that the rotation direction of the wheels 5a to 5d on which the two tire sensors 2 are installed is reversed, swaps the wheel positions of the two tire sensors 2. Then, the second transmitting / receiving unit 31 notifies the tire sensors 2 of the wheel position determination state (see step S365 in Figure 6, etc.).
[0114] When the left and right wheels 5a to 5d rotate, the direction of rotation of wheels 5a to 5d reverses. By using this to determine the wheel position, the series of processes performed by the tire sensor 2 can be avoided, thereby reducing the power consumption of the tire sensor 2.
[0115] (Modified version of the embodiment) As described in the above embodiment, it is desirable that the in-vehicle unit 3, upon receiving a frame, transmits a response signal to the tire sensor 2 with the wheel position identification state added via the second transmitting / receiving unit 31, but it is not limited to this. The in-vehicle unit 3 may also transmit signals other than the response signal with the wheel position identification state added.
[0116] As described in the above embodiment, it is desirable that the in-vehicle device 3 changes the wheel position determination state to wheel position undetermined if the vehicle 1 remains stationary for longer than a predetermined parking determination time after the wheel position has been determined, but this is not required.
[0117] As described in the above embodiment, it is desirable that the tire sensor 2 changes its status flag to "wheel position undetermined" if the slow-moving or stopped state continues for more than a predetermined reference time after notification of wheel position determination, but this is not required. The tire sensor 2 determines the vehicle speed from the output of the acceleration sensor 22 and determines whether the vehicle 1 is moving or not based on that vehicle speed, but this is not limited to this. The tire sensor 2 may also calculate centrifugal acceleration by removing the gravitational acceleration component from the output of the acceleration sensor 22 and determine whether the vehicle 1 is moving or not based on that centrifugal acceleration. The notification of the wheel position determination status from the on-board unit 3 to the tire sensor 2 is not limited to notifying whether the wheel position is determined or undetermined, but may also notify only one of them.
[0118] As described in the above embodiment, it is desirable that the tire sensor 2 creates a frame indicating a unidirectional command when the vehicle 1 is moving and a frame indicating a bidirectional command when the vehicle is moving slowly or stopped, but this is not required.
[0119] As described in the above embodiment, it is desirable that the tire sensor 2 be configured to determine whether or not the wheels have been removed or attached when the vehicle is moving slowly or stopped, but this is not required. For example, the tire sensor 2 may be configured to determine whether or not the wheels have been removed or attached when the vehicle is moving slowly or stopped. Alternatively, the tire sensor 2 may not be configured to determine whether or not the wheels have been removed or attached when the vehicle is moving slowly or stopped. Furthermore, the notifications such as the wheel removal / installation flag from the tire sensor 2 to the in-vehicle unit 3 are not limited to notifying whether wheel removal / installation has not been performed or is unknown, but may also be configured to notify only one of the two. The same applies when determining whether or not wheel removal / installation has been performed.
[0120] As described in the above embodiment, if there is a possibility of attaching and detaching the wheels, and the rotation directions of the wheels 5a to 5d on which the two tire sensors 2 are installed are reversed, it is desirable to swap the wheel positions of the two tire sensors 2, but this is not required. In this case, since it is not necessary to detect the rotation direction of the wheels 5a to 5d, the acceleration sensor 22 may be composed of a single-axis acceleration sensor.
[0121] In the above-described embodiment, it is determined whether or not the wheels of the running wheels have been removed or attached, but the system is not limited to this. For example, it may also be determined whether or not the wheels of the spare wheels have been removed or attached in addition to the running wheels.
[0122] (Other embodiments) This disclosure is written in accordance with the embodiments described above, but is not limited to those embodiments and includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.
[0123] For example, while the tire sensor 2 was described as being attached to the air injection valve, it may be installed in other locations. For example, it may be installed in place of the valve cap or on the tread inside the tire.
[0124] Furthermore, in the above embodiment, unidirectional commands are included in the frame while the vehicle 1 is in motion, and bidirectional commands are included in the frame while the vehicle is stopped. However, these commands do not necessarily have to be represented as data; they may be in a form where the absence of data effectively indicates each command. For example, only one of the unidirectional or bidirectional commands may be represented as data, and the in-vehicle unit 3 may determine that the other command is being represented if that command is not included in the frame. Specifically, only bidirectional commands may be stored in the frame, and the in-vehicle unit 3 may determine that a unidirectional command is being represented if the frame does not contain any bidirectional commands.
[0125] Furthermore, in the above embodiment, the reception processing on the in-vehicle unit 3 is stopped when the power switch is turned off. However, the in-vehicle unit 3 may also perform reception processing periodically or irregularly even when the power switch is turned off.
[0126] Furthermore, although the above embodiment shows an example in which the tire sensor 2 is provided on all of the wheels 5a to 5d, this disclosure can be applied to a TPMS that is provided on at least one wheel.
[0127] Furthermore, in the above embodiment, the portion of the TPMS provided on the vehicle body 6 side is collectively described as the on-board unit 3, but the on-board unit 3 does not necessarily have to be a single configuration. For example, the second transceiver unit 31 that performs the transmission and reception function and the second microcomputer 33 that performs the tire pressure detection function may be provided in separate locations.
[0128] In the embodiments described above, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where they are explicitly stated to be essential or where they are clearly considered essential in principle.
[0129] In the embodiments described above, if numerical values such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiment is not limited to those specific numbers unless explicitly stated as particularly essential or clearly limited to a specific number in principle.
[0130] In the embodiments described above, when referring to the shape, positional relationships, etc. of the components, the definition is not limited to those shapes, positional relationships, etc., unless otherwise specifically stated or when the definition is fundamentally limited to a particular shape, positional relationship, etc.
[0131] The control unit and its method of this disclosure may be implemented in a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. The control unit and its method of this disclosure may be implemented in a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. The control unit and its method of this disclosure may be implemented in one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. The computer program may also be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium. [Explanation of Symbols]
[0132] 2 Tire Sensors 22 Accelerometer 23. First Microcomputer (First Control Unit) 24 First Transmitter / Receiver Unit 3 Onboard equipment 31 Second Transmitter / Receiver Unit 32. Second Microcomputer (Second Control Unit) 11a~11d Wheel angle sensor
Claims
1. A wheel position detection device applied to a vehicle (1) in which a plurality of wheels (5a to 5d), including tires, are attached to a vehicle body (6), Multiple tire sensors (2) are provided on each of the multiple wheels (5a to 5d) and transmit frames to which unique identification information is attached, The vehicle includes an on-board unit (3) provided on the vehicle, Each of the multiple tire sensors includes an acceleration sensor (22) that outputs a detection signal corresponding to the acceleration that changes with the rotation of the wheel, a first control unit (23) that performs a series of processes to determine the rotation angle indicating the position of the tire sensor in the circumferential direction of the wheel as a first rotation angle based on the detection signal of the acceleration sensor when the acceleration sensor's detection signal is greater than or equal to a predetermined value, and to notify the in-vehicle unit of the first rotation angle, and a first transmitting / receiving unit (24) that transmits the frame and receives the response signal transmitted from the in-vehicle unit. The in-vehicle unit includes a second transmitting / receiving unit (31) that receives the frame and transmits the response signal, and a second control unit (33) that identifies the wheel position on which the tire sensor is installed based on the output signals of wheel angle sensors (11a to 11d) provided corresponding to each of the plurality of wheels and notification of the first rotation angle. The second control unit notifies the tire sensor of the wheel position determination status, indicating whether the wheel position is determined or not, via the second transmitting / receiving unit. The first control unit is a wheel position detection device that stops the execution of the series of processes in the driving state when it is notified that the wheel position has been determined.
2. The wheel position detection device according to claim 1, wherein when the in-vehicle unit receives the frame, the second transmitting / receiving unit transmits the response signal to the tire sensor with the wheel position identification state added to it.
3. The wheel position detection device according to claim 1 or 2, wherein the second control unit changes the wheel position determination state to wheel position undetermined if the vehicle remains stationary for longer than a predetermined parking determination time after the wheel position has been determined.
4. The wheel position detection device according to claim 3, wherein the first control unit determines whether to perform the series of processes by referring to a status flag indicating whether the wheel position is determined or not in the driving state, and sets the status flag to "determined wheel position" when the determination of the wheel position is notified, while if the state in which the detection signal of the acceleration sensor is less than the specified value continues for a predetermined reference time after the determination of the wheel position is notified, the status flag is changed to "undetermined wheel position".
5. The wheel position detection device according to claim 1 or 2, wherein the first control unit creates the frame indicating a unidirectional command when transmitting the frame from the first transmitting / receiving unit in the driving state, and creates the frame indicating a bidirectional command requesting the response signal when the detection signal of the acceleration sensor falls below the specified value.
6. The first control unit determines whether or not the wheel has been removed from the vehicle body when the detection signal from the acceleration sensor is less than the specified value, and transmits the frame indicating the determination result from the first transmitting / receiving unit. The wheel position detection device according to claim 1 or 2, wherein the second control unit determines whether it is necessary to specify the wheel position, including the determination result when the second transmitting / receiving unit receives the frame indicating the determination result while the vehicle is in motion, and if it is determined that it is not necessary to specify the wheel position, the second transmitting / receiving unit notifies the tire sensor of the wheel position specification state indicating that the wheel position has been determined.
7. The wheel position detection device according to claim 6, wherein the first control unit determines whether or not the wheel has not been removed from the vehicle body when the detection signal of the acceleration sensor is less than the predetermined value, and transmits the frame indicating the determination result from the first transmitting / receiving unit.
8. The acceleration sensor is capable of detecting the radial acceleration of the wheel as a first acceleration and the circumferential acceleration of the wheel as a second acceleration. The first control unit detects the rotation direction of the wheels based on the first acceleration and second acceleration detected by the acceleration sensor in the driving state, and transmits the frame including the detection result from the first transceiver unit. The wheel position detection device according to claim 6, wherein the second control unit, when the determination results from the two tire sensors indicate that there is a possibility of removing the wheel, and the determination results from each of the two tire sensors indicate that the direction of rotation of the wheel is reversed from the previous direction, swaps the wheel positions of the two tire sensors and notifies the tire sensors of the wheel position determination state via the second transmitting / receiving unit.